Conventional surge material is a non-absorbent material used in absorbent articles such as diapers to provide intake of fluid and some temporary storage before fluid is absorbed by an absorbent material or superabsorbent material. Many high-absorbency materials are unable to absorb a liquid at the rate at which liquid is applied to absorbent composites during use. Accordingly, a relatively high concentration of fibrous surge material is desirable to temporarily hold the liquid until the high-absorbency material can absorb it. Conventional surge material is also used to spread the fluid over more surface area of the absorbent material thereby increasing absorbency efficiency.
By providing temporary storage of fluids the surge material keeps the fluid from returning (flowback) through a body-side liner of the diaper, or other absorbent article, and contacting the skin. The surge material increases absorption efficiency and decreases flowback caused by the slower-absorbing absorbent material. Examples of particular surge materials may be found in U.S. Pat. No. 5,490,846 to Ellis et al. and in U.S. Pat. No. 5,364,382 to Latimer.
Conventional surge materials do not include superabsorbent materials. Instead, superabsorbents are commonly used in the absorbent core to increase its absorption capacity. A wide variety of superabsorbent materials are known to those skilled in the art. See, for example, U.S. Pat. No. 4,076,663 issued Feb. 28, 1978 to Masuda et al, U.S. Pat. No. 4,286,082 issued Aug. 25, 1981 to Tsubakimoto et al., U.S. Pat. No. 4,062,817 issued Dec. 13, 1977 to Westerman, and U.S. Pat. No. 4,340,706 issued Jul. 20, 1982 to Obayashi et al.
Methods of applying superabsorbent material onto fibrous absorbent material structures are also known to those skilled in the art. U.S. Pat. No. 6,022,610 issued 08 Feb. 2000 to Van Phan et al. describes the problems that occur in known application methods. For instance, applying a liquid superabsorbent precursor onto a fibrous structure may result in the liquid precursor migrating through the fibrous material. This migration of superabsorbent liquid precursor may result in diminished absorption due to the restriction of the swelling of the superabsorbent material. Gel-blocking may also occur with applied superabsorbent material. Gel-blocking occurs when particles of high-absorbency material deform during swelling and block the interstitial spaces between the particles, or between the particles and absorbent fibers, thus preventing the flow of liquid through the interstitial spaces.
There is a need for surge material with improved intake properties and having permanent storage properties, which can also reduce flowback and leakage of urine, or other fluid, from the absorbent article to the user's skin.